1. Field of the Invention
The present invention relates to slide fasteners, and more particularly to slide fasteners having a reinforced separating end stop.
2. Description of the Prior Art
Numerous slide fasteners are known to the art such as the type having a separating end stop attached to a pair of stringer tapes provided with opposed interengaging elements operable by means of a slider. When edges of an article are joined by a slide fastener, the tensional stresses are more or less uniformily distributed along the entire length of the stringer tapes because of the large number of closely positioned interengaging elements. However, when the slide fastener is joined only by means of the separating end stop or additionally by means of only a limited number of interengaging elements adjacent the separating end stop, great tensional stresses are caused to occur along the ends of the stringer tapes in the area of the separating end stop which over a limited period of use causes wear or fraying of the material forming the stringer tapes.
Attempts by the prior art to resolve the recognized problem of wear or fraying of the material forming the stringer tapes in the area adjacent the end stops have been limited because of recognized requirements that the slider be permitted to operate over the end stops for disengagement, as well as the need to perserve esthetic quality of the fastener.
Although the prior art has recognized the need to reinforce stringer tapes in the area of wear adjacent the end stop members of a slide fastener, the requirements of functionality and esthetic appeal have presented obstacles which have limited commercial acceptance of proposed solutions to this problem of wear.
Accordingly, although great improvements have been made in the simplicity, effectiveness, and limited breakage of the slide and interengaging elements forming a slide fastener, the useful life thereof remains limited because of damage by tensional stresses in the area of the end stop portion of the stringer tapes.
One attempt to reinforce a slide fastener in the area of the end stop is that disclosed in U.S. Pat. No. 3,872,551. Here, the end stop components are secured to the stringer tapes by means of tape reinforcing flaps which are laminated over the surface of opposite sides of the tapes. The reinforcing flaps comprise a grid effect formed of a framed border having rib elements disposed therein. Although effective reinforcing of the stringer tapes ends may be accomplished by this device, the reinforcing flaps are merely joined by a laminated member of limited thickness over the surface of the stringer tapes to the end stop members such that tensional forces, although limited somewhat, remain in the plane of the material forming the stringer tapes adjacent the end stop.
Another attempt to reinforce a slide fastener in the area of the end stop is that disclosed in British Specification No. 1,077,986 wherein reinforcement is achieved by means of gap ribs extending laterally of the taps in a zig-zag configuration joining to a reinforcing grid. Because of the tendency of the material forming the stringer tapes to return to a horizontal plane, gaps tend to appear along the side walls of the gap ribs resulting in poor adhesion with the stringer tape. Thus, although the gap ribs of this British Specification provide a somewhat stronger union between the reinforcement grid and stop end elements by reason of increased thickness, wear caused by the thicker ribs rubbing against unsecured portions of the stringer tapes tending to return to a normal plane presents a serious defect to this attempted solution of the problem.
It has now been found that by practice of the present invention, there is provided a simple, effective and esthetic solution to the problem of wear by tensional forces in the immediate area of stringer tapes adjacent the end stop elements.